This invention relates to a mobile -communication system which allows hand-over including a function by which a set of links including an up-link (Up-link) and a down-link (Down-link) having different communication capacities can be used as one communication channel (hereinafter referred to as an asymmetrical communication channel) using frequency channel sharing or time slot sharing in which a multiple connection system such as a TDMA (TDMA; Time divided Multiple Access; time divided multiple access) system or a time divided CDMA (CDMA; Code Division Multiple Access; code division multiple access) system is used.
A mobile communication system is principally composed of mobile stations such as, for example, mobile car-carried communication apparatus or mobile portable communication apparatus, and radio base stations which communicate with the mobile stations by radio channels. In such a mobile communication system as just described, sharing of the same radio frequency spectrum by different radio systems hereinafter referred to as frequency channel sharing) is sometimes effected between an FDMA (FDMA; Frequency Division Multiple Access; frequency division multiple access) system or a TDMA system and a CDMA system. It is to be noted that, in the CDMA system, frequency channel sharing between different codes has already been put into practical use. Further, hand-over in those systems is known already.
Here, a mobile communication system of time slot sharing wherein a TDMA signal and a time divided CDMA signal are shared in a same time slot is disclosed in the official gazette of Japanese Patent Laid-Open Application No. Hei 8-130766 already filed for patent separately and so forth. However, those documents do not describe an asymmetrical communication channel between up- and down-links or hand-over in high speed data transmission.
Meanwhile, a technique of a mobile communication system of time slot sharing and frequency channel sharing wherein a TDMA signal and a time divided CDMA signal are used in a same time slot and synchronization between radio base stations in which a semi-fixed communication apparatus (hereinafter referred to as WLL station) by a wireless local loop (Wireless Local Loop; hereinafter referred to as WLL) and so forth have already been filed for patent by Japanese Patent Application No. Hei 9-188356 and so forth. However, those documents do not recite an asymmetrical communication channel wherein an up-link and a down-link have different communication capacities or hand-over in high speed data transmission.
Furthermore, also a technique of a mobile communication system suitable for a multi-media radio environment having an asymmetrical communication channel is filed for patent separately by Japanese Patent Application No. Hei 9-164817. However, in the document, hand-over in high speed data transmission is not taken into consideration.
Meanwhile, as a mobile communication system wherein a plurality of CDMA signals are shared, U.S. Pat. No. 5,363,403 is known. However, the specification of the patent does not recite a method of handling a time divided CDMA signal. While also U.S. Pat. No. 5,511,068 is known as another mobile communication system, the document relates to an adaptive filter for a time divided CDMA signal system, and the specification of it recites neither that frequency channel sharing of a CDMA signal and a TDMA signal is performed in one time slot nor hand-over in high speed data transmission.
Further, as a document which handles hand-over, International Publication No. WO96/06512 is known. However, the invention of the document handles hand-over in a cellular (Cellular) communication system, and does not recite a case wherein time slot sharing of a time divided CDMA signal and a TDMA signal is performed in one time slot or a mobile communication system which has an asymmetrical communication channel.
Furthermore, as a document which relates to a communication system wherein a TDMA technique is applied to a CDMA communication system, also U.S. Pat. No. 5,410,568 is known. This patent places a synchronization code (Synchronization-code) at the top of a frame of CDMA communication, that is, at the top of a burst, but does not introduce a time divided CDMA system using a TDMA control channel in order to effect frame synchronization setting, nor recites coexistence with a TDMA system. In other words, the patent does not intend sharing between a TDMA system and a time divided CDMA system using a TDMA frame. Further, in this patent, no attention is paid at all to a communication channel wherein the communication capacities of an up-link and a down-link are asymmetrical, and hand-over in high speed data transmission is not recited either.
It is to be noted that, in addition to the documents mentioned above, the official gazette of Japanese Patent Laid-Open Application No. Hei 6-22364, the official gazette of Japanese Patent Laid-Open Application No. Hei 7-322332, the official gazette of Japanese Patent Laid-Open Application No. Hei 8-154269, the official gazette of Japanese Patent Laid-Open Application No. Hei 8-280056 and so forth are known.
However, while the official gazette of Japanese Patent Laid-Open Application No. Hei 6-22364 mentioned above discloses a technique of hand-over for a TDMA cellular system, it is quite silent about an asymmetrical channel wherein an up-link and a down-link have different transmission capacities or a matter regarding hand-over in high speed data transmission.
In the meantime, while the official gazette of Japanese Patent Laid-Open Application No. Hei 7-322332 discloses a technique regarding reception of other base station signals in a silence period in a cellular system of the FDMA system, the TDMA system or the CDMA system or hand-over based on such reception, it does not recite an asymmetric channel wherein an up-link and a down-link have different transmission capacities or hand-over in high speed data transmission.
On the other hand, while the official gazette of Japanese Patent Laid-Open Application No. Hei 8-154269 discloses a technique wherein, in a mobile communication system, strengths of radio signals from radio base stations are measured and order numbers are applied to the radio signals in the descending order of the radio signal strengths and then the order is correlated with the order of hand-over and a candidate for hand-over is selected based on the correlation, it does not recite a communication system of an asymmetric channel wherein an up-link and a down-link have different transmission capacities or hand-over in high speed data transmission.
Further, while the official gazette of Japanese Patent Laid-Open Application No. Hei 8-280056 discloses a technique wherein, in a cellular system of the TDMA system or the CDMA system, a data buffer is provided in a radio base station and synchronism is established between the radio base station and an adjacent base station to realize instantaneous disconnection-free hand-over, it does not recite mobile communication having an asymmetric channel wherein an up-link and a down-link have different transmission capacities or hand-over in high speed data transmission.
Such various mobile communication systems which include one or more radio base stations which communicate with a plurality of mobile stations by radio channels and use the TDMA system and the time divided CDMA system as described above are conventionally known. Also in such mobile communication systems as described above, the demand for introduction of high speed data transmission is increasing. However, a mobile communication system which can sufficiently meet the demand has not been realized as yet.
Also it is demanded to introduce a communication channel wherein an up-link and a down-link have different communication capacities in order to make a mobile communication system cope with multi-media.
Furthermore, also in such a mobile communication system as described above, it is necessary to introduce hand-over means for allowing smooth hand-over in high speed data transmission.
The present invention has been made to solve such problems as described above. It is an object of the present invention to introduce high speed data channels into a TDMA signal and time divided CDMA signal coexisting mobile communication system and to realize a mobile communication system of the type wherein communication links wherein an up-link and a down-link have different communication capacities are allocated as a set of communication channels, which allows hand-over and copes with multi-media.
A mobile communication system according to the present invention is constructed such that it includes a mobile switching center which has TDMA signals and time slot sharing and frequency channel sharing time divided CDMA signals and has a controlling function of allocating the signals on a time base and a frequency base, and mobile stations and a radio base station or stations connected to the mobile switching center are radio connected to each other by a multiple connection system such that information of time slots in frames of down-links transmitted from two adjacent ones of the radio base stations to one of the mobile stations has serial numbers provided by the mobile switching center to which the radio base stations are connected. By this construction, hand-over between radio base stations can be realized by a unified process based on the serial numbers.
A mobile communication system according to the present invention is constructed such that each of the mobile stations has a function of detecting serial numbers included in information of time slots in frames of two down-links transmitted thereto from two radio base stations.
A mobile communication system according to the present invention is constructed such that the mobile switching center has a function of repetitively setting serial numbers included in information of time slots in a frame of a signal transmitted from the mobile switching center to a radio base station for each multi-frame number of a radio channel or for each integral number of times the multi-frame number.
A mobile communication system according to the present invention is constructed such that each of the mobile stations has a function of receiving, detecting and comparing serial numbers included in information of time slots in a frame of a signal being transmitted from the radio base station (switching source base station) with which the mobile station is communicating and serial numbers included in information of time slots in a frame of a signal being transmitted from the radio base station (switching destination base station) to which the communication is to be re-connected as a result of a movement of the mobile station, producing a repetition code based on difference information between the two serial numbers and transmitting the repetition code to the mobile switching center via the switching source base station.
A mobile communication system according to the present invention is constructed such that the repetition code is a negative number when the signal transmitted from the switching destination base station arrives later than the signal transmitted from the switching source base station, but the repetition code is a positive number when the signal transmitted from the switching destination base station arrives earlier than the signal transmitted from the switching source base station.
A mobile communication system according to the present invention is constructed such that each of the mobile stations has a function of receiving, detecting and comparing, upon hand-over, serial numbers included in information of time slots in a frame of a signal being transmitted from the switching source base station and serial numbers included in information of time slots in a frame of a signal being transmitted from the switching destination base station, and abandoning, when the signal transmitted from the switching destination base station arrives later than the signal transmitted from the switching source base station, information in a number of time slots of a signal received newly from the switching destination base station upon hand-over equal to a number indicated by contents of a repetition code based on difference information between the two serial numbers. By this construction, adjustment of an information delay when the signal of the switching destination base station arrives later than the signal of the switching source base station is performed by the mobile station, and discontinuity of information which occurs upon hand-over can be eliminated readily.
A mobile communication system according to the present invention is constructed such that an switching center of the ATM type is used for the mobile switching center, and the mobile switching center has a function of realizing numbering of serial numbers included in information of time slots in a frame by newly adding a header to the top of an ATM packet.
A mobile communication system according to the present invention is constructed such that the mobile switching center has a function of constructing, when the number of information bits which can be transmitted by one time slot of a radio channel is smaller than the number of information bits for one packet of public network packets transmitted by a public network, packets each having information obtained by dividing information of the public network packets for each time slot information bit of the radio channel and transmitting the packets to a radio base station.
A mobile communication system according to the present invention is constructed such that the mobile switching center has a packet information amount variation function of transmitting, when the number of information bits which can be transmitted by one time slot of a radio channel is larger than the number of information bits for one packet of public network packets, information of the public network packets as it is to a radio base station without dividing the information of the public network packets.
A mobile communication system according to the present invention is constructed such that an switching center interface of each of the radio base stations is of the ATM type.
A mobile communication system according to the present invention is constructed such that each of the mobile stations has a function of receiving, detecting and comparing, upon hand-over, serial numbers included in information of time slots in a frame of a signal being transmitted from a switching source base station and serial numbers included in information of time slots in a frame of a signal being transmitted from a switching destination base station and producing a repetition code based on difference information between the two serial numbers, and each of the radio base stations has a function of holding, when the radio base station becomes the mobile destination base station, if the signal transmitted arrives earlier than the signal transmitted from the switching source base station, information in a number of time slots of the signal transmitted to the mobile station already equal to a number indicated by contents of the repetition code in response to an instruction of the repetition code upon hand-over, and successively transmitting, simultaneously with hand-over, signals to the mobile station beginning with the held information of the time slots. By this construction, when the signal of the switching destination base station arrives earlier than the signal from the switching source base station, the switching destination base station re-sends information of the last time slot of the preceding frame by a number indicated by contents of the repetition code to make the delays of information from the radio base stations at the mobile station equal to each other, and consequently, discontinuity of information which arises upon hand-over can be eliminated readily.
A mobile communication system according to the present invention is constructed such that it includes a mobile switching center which has TDMA signals and time slot sharing and frequency channel sharing time divided CDMA signals and has a controlling function of allocating the signals on a time base and a frequency base, and mobile stations and a radio base station or stations connected to the mobile switching center are radio connected to each other by a multiple connection system while the mobile stations having a high speed data transmission function can be radio connected to the radio base stations also by high speed data channels such that information of time slots of the high speed data transmission channels being transmitted in each time slot in frames of two down-links transmitted from two adjacent ones of the radio base stations to one of the mobile stations has serial numbers provided by the mobile switching center to which the radio base stations are connected. By this construction, hand-over between radio base stations upon high speed data transmission can be realized by a unified process based on the serial numbers.
A mobile communication system according to the present invention is constructed such that each of the mobile stations has a function of detecting serial numbers included in information of micro slots of high speed data transmission channels transmitted in each time slot in frames of two down-links transmitted thereto from two radio base stations.
A mobile communication system according to the present invention is constructed such that the mobile switching center has a function of repetitively setting serial numbers included in information of micro slots of high speed data transmission channels transmitted in each time slot in a frame of a signal transmitted from the mobile switching center to a radio base station for each multi-frame number of a radio channel or for each integral number of times the multi-frame number.
A mobile communication system according to the present invention is constructed such that each of the mobile stations has a function of receiving, detecting and comparing serial numbers included in information included in a number of micro slots of a high speed data transmission channel transmitted in each time slot in a frame of a signal being transmitted from a switching source base station and serial numbers included in information included in a number of micro slots of a high speed data transmission channel transmitted in each time slot in a frame of a signal being transmitted from a switching destination base station, producing a repetition code based on difference information between the two serial numbers and transmitting the repetition code to the mobile switching center via the switching source base station.
A mobile communication system according to the present invention is constructed such that each of the mobile stations has a function of receiving, detecting and comparing, upon hand-over, serial numbers included in information of micro slots of a high speed data transmission channel transmitted in each time slot in a frame of a signal being transmitted from a switching source base station and serial numbers included in information of micro slots of a high speed data transmission channel transmitted in time slots in a frame of a signal being transmitted from a switching destination base station and abandoning, when the signal transmitted from the switching destination base station arrives later than the signal transmitted from the switching source base station, information of a number of micro slots of a signal received newly from the switching destination base station upon hand-over equal to a number indicated by contents of a repetition code based on difference information between the two serial numbers. By this construction, adjustment of an information delay when the signal of the switching destination base station upon high speed data transmission arrives later than the signal of the switching source base station is performed by the mobile station, and continuity of information which arises upon hand-over in high speed data transmission can be eliminated readily.
A mobile communication system according to the present invention is constructed such that each of the mobile stations has a function of receiving, detecting and comparing, upon hand-over, serial numbers included in information of micro slots- of a high speed data transmission channel transmitted in each time slot in a frame of a signal being transmitted from a switching source base station and serial numbers included in information of micro slots of a high speed data transmission channel transmitted in each time slot in a frame of a signal being transmitted from a switching destination base station and producing a repetition code based on difference information between the two serial numbers, and each of the radio base stations has a function of holding, when the radio base station becomes the mobile destination base station upon hand-over of the mobile station, if the signal transmitted therefrom arrives earlier than the signal transmitted from the switching source base station, information of a number of micro slots of the signal transmitted to the mobile station already equal to a number indicated by contents of the repetition code in response to an instruction of the repetition code upon hand-over, and successively transmitting, simultaneously with hand-over, signals to the mobile station beginning with the held information of the micro slots. By this construction, when the signal of the switching destination base station upon high speed data transmission arrives earlier than the signal from the switching source base station, the switching destination base station re-sends information of the last micro slots of the preceding frame by a number indicated by contents of the repetition code to make the delays of information from the radio base stations at the mobile station equal to each other, and consequently, discontinuity of information which arises upon hand-over in high speed data transmission can be eliminated readily.
A mobile communication system according to the present invention is constructed such that the mobile switching center has a function of transmitting a repetition code from a mobile station received via the switching source base station to the switching destination base station simultaneously with determination of hand-over.
A mobile communication system according to the present invention is constructed such that it includes a mobile switching center which has TDMA signals and time slot sharing and frequency channel sharing time divided CDMA signals and has a controlling function of allocating the signals on a time base and a frequency base, and mobile stations and a radio base station or stations connected to the mobile switching center are radio connected to each other by a multiple connection system while each of the radio base stations has a function of applying, when the radio base station is to transfer information included in a time slot received from one of the mobile stations to the mobile switching center, a serial number associated with a multi-frame of a radio channel to the information from the mobile station. By this construction, the mobile switching center can discriminate the order of information transmitted by the mobile station, and it can be eliminated that, upon hand-over, the order of information to be transmitted from the mobile switching center to a public network is mistaken.
A mobile communication system according to the present invention is constructed such that the mobile switching center has a function of detecting serial numbers included in information of a time slot transferred from a radio base station thereto and associated with a multi-frame of a radio channel.
A mobile communication system according to the present invention is constructed such that each of the radio base stations has a function of setting serial numbers included in information of a time slot transferred from a radio base station thereto and associated with a multi-frame of a radio channel repetitively for each multi-frame number of the radio channel or for each integral number of times the multi-frame number.
A mobile communication system according to the present invention is constructed such that each of the radio base stations has a function of adding serial numbers included in information of a time slot transferred to the mobile switching center and associated with a multi-frame of a radio channel as a header to the top of an information packet to be transferred to the mobile switching center.
A mobile communication system according to the present invention is constructed such that the mobile switching center has a function of checking, upon hand-over, serial numbers included in headers of information packets transferred thereto from two radio base stations and transferring the information packets in order to a public network so that the serial numbers may be arranged in a correct order.
A mobile communication system according to the present invention is constructed such that a mobile station employed therein includes storage means for storing information included in a time slot received from a radio base station or information included in micro slots in the time slot, and control means for controlling, upon -hand-over, the storage means to abandon information stored therein by a number designated by contents of a repetition code. By this construction, when hand-over is to be performed, since it is only required to set the storage means and the control means for controlling the storage means with contents of the repetition code, hand-over control when a signal of a switching source base station arrives later than a signal of a switching destination base station can be performed readily in the mobile station.
A mobile communication system according to the present invention is constructed such that a radio base station employed therein includes storage means for storing information included in a time slot transmitted therefrom immediately prior to hand-over or information included in micro slots in the time slot, and control means for controlling the storage means to store information transmitted immediately prior to the hand-over by a number designated by contents of a repetition code and re-send the information stored in the storage means upon the hand-over. By this construction, also when the information of the switching destination base station arrives earlier than the information of the switching source base station, it can be prevented that, upon hand-over, a mobile station receives continuous information while the information partially drops.
A mobile communication system according to the present invention is constructed such that it includes a mobile switching center which has TDMA signals and time slot sharing and frequency channel sharing time divided CDMA signals and has a controlling function of allocating the signals on a time base and a frequency base, and mobile stations and a radio base station or stations connected to the mobile switching center are radio connected to each other by a multiple connection system while the mobile switching centers are directly connected to each other by an additional communication line without having the public network interposed therein. By this construction, by performing setting of a header which passes through the additional communication line which directly connects the mobile switching centers to each other and the mobile switching centers, occurrence of hand-over can be made independent of the public network.
A mobile communication system according to the present invention is constructed such that, when hand-over between a switching source base station and a switching destination base station connected to mobile switching centers different from each other is performed, information from the switching destination base station which is communicating with a mobile station after the hand-over is performed is transmitted from the mobile switching center to which the switching destination base station is connected to the public network via the additional communication line and the mobile switching center to which the switching source base station is connected.
A mobile communication system according to the present invention is constructed such that, after the communication of the information from the switching destination base station which is transmitted from the mobile switching center to which the switching destination base station is connected to the public network via the additional communication line and the mobile switching center to which the switching source base station is connected comes to an end once, when the communication is to be resumed, the information from the mobile station is directly transmitted from the switching destination base station to the public network via the mobile switching center to which the switching destination base station is connected.
A mobile communication system according to the present invention is constructed such that a plurality of mobile switching centers connected by the additional communication line belong to different operators from each other. Also hand-over between radio base stations connected to mobile switching centers which belong to different operators from each other in this manner can be treated similarly to hand-over between radio base stations which belong to a same operator.
A mobile communication system according to the present invention is constructed such that an switching center of the ATM type is used for the plurality of mobile switching centers connected to each other by the additional communication line.
A mobile communication system according to the present invention is constructed such that the additional communication line by which the plurality of mobile switching centers are connected to each other is of the ATM type.
A mobile communication system according to the present invention is constructed such that, when a mobile station is still busy after handed over between a plurality of radio base stations which belong to a plurality of mobile switching centers, information -from a switching destination base station which is communicating with the mobile station at present is transmitted from the mobile switching center to which a switching source base station is connected to the public network via the plurality of mobile switching centers and a plurality of additional communication lines by which the plurality of mobile switching centers are connected to each other passing the mobile switching center to which the switching destination base station.